What is it about some sounds that gives them clear pitch, while other sounds come across as pitchless noise? The simple answer is that pitched sounds have a steady repetition rate, or frequency, that the ear can pickup up on and identify. Noisy sounds are more chaotic and irregular; the ear does not recognize a steady frequency.
A deeper look at the question reveals a bit more complexity: some sounds – many sounds, in fact – have one or more steady frequencies, but those steady frequencies are mixed in with some amount of noisy irregularity. In fact, virtually all musical sounds aside from pure synthesizer tones have some unpitched components. For instance, the flautist blows across the hole in the mouthpiece and a pattern of air flow develops at the edge of the hole which sets up a clear tone in the resonant air column, and that’s most of what we hear. But there inevitably is also some chaotic turbulence at the blow-hole edge as the air stream rushes across. While the air column resonance draws the listener’s ear with its clear, pitched tone, the unpitched edge-turbulence sound is still present. It’s typically much quieter, usually not consciously noted, but it can often be heard as a sort of breathy overlay. Even unnoticed it contributes meaningfully to the sound quality ̶ a subtle unpitched component adding a bit of character to the otherwise clearly pitched flute tone.
The most famous maker of noise instruments was the Italian Futurist Luigi Russolo, working in the 1920s. He built and composed for a series of instruments which he called Intonarumori – “noise intoners” – designed to have some degree of recognizable pitch in otherwise very noisy sounds. Many of them used strings and membranes agitated in ways that brought out strong noise components. The original instruments no longer survive, but recreations have been built, based upon written records.
While I haven’t made a noise orchestra to rival Luigi’s, I have made quite a few instruments in this in-between territory myself. Several but not all have been flute-like instruments. A few examples:
The breathy component of flute tone described above interests me, so I recently made a flute-like instrument specifically to bring it out. This breath flute (as I’ve been calling it) is an end-blown flute set up in a way that makes it hard to get the strong air column resonance that flautists learn to produce with such clarity. Instead, it yields a much less focused tone in which the pitch of the air column resonance can be heard, but half-buried in a breathy, unpitched edge-turbulence sound. The lack of a strong resonance in the air column means that this flute is pretty quiet, so a tiny electret microphone is fitted into a hole in the pipe where it can listen directly to the sound within. In addition to reinforcing the volume, the mic brings out a distinctive inner-air-column sound quality. When the breath flute is heard alone, the listener’s ear recognizes the pitch of the air column resonance and easily follows melodies the flute plays, despite the presence of all that unpitched information in the tone. It’s an evocative effect, the flute tone in among the all the windy breathiness, the pitched and the unpitched somehow moving together and integral to one another. But in more crowded musical contexts, as when other instruments are present, it becomes harder to sort out the flute’s sound. Then it may no longer be possible to follow the flute’s melody, and the effect in general is noisier, less musically meaningful, and in most cases less appealing.
Another instrument that mixes tone and noise is my waffle-gurgle flute. It’s a flute-like pipe with toneholes, but instead of blowing across an opening to create a clear edge-tone, the player blows through something similar to the comic novelty noise maker known as a rubber razzer. “Den ve Heil! Pphhttt! Heil! Pphhttt! Right in der führer’s face!” … If you If know this World War Two song from the Spike Jones band, then you know the sound of a rubber razzer. For the waffle-gurgle flute the razzer-like component is basically a sort of droopy-floppy latex tube a couple of inches long, easily made from a balloon neck. The neck droops into what would normally be the blowing end of the flute pipe. When you blow through it, the razzer flaps around crazily trying to make the pphhttt sound within the restricted space of the tube, creating a chaotic raspy sound. From out of the generalized agitation of the air that results, the air column within the pipe selectively reinforces its own natural resonance frequencies. As with standard flutes, the pitch of this resonance depends on the length of the tube and the configuration of open and closed tone holes. What the listener hears is the razzy sound, as crazy and chaotic as ever, but with the clearly pitched tone of the air column resonance highlighted enough to give it an identifiable pitch. By the usual flute fingering techniques you can play melodies.
A closely related instrument, the water gurgle flute, has a similar flute-like body, but instead of the razzer there’s an arrangement for making water-bubbling sounds. A small enclosed vessel at the bottom of the flute holds a bit of water. A blow tube enters the chamber and extends into the water. By blowing through the blow tube the player can agitate the water the same way a child in a fast food restaurant uses a straw to make bubbling sounds in a drink. The flute pipe rises from this chamber. The end of the pipe that would normally be the mouthpiece extends down into the chamber, stopping a little above the water level. As with the waffle-gurgle described above, the air column selectively reinforces its resonance tones from amid the generalized-frequencies of the bubbling noise, and a tiny mic in the air column picks this up. An odd feature of the instrument is that the pipe has to point upward, opposite to the usual flute positioning. What would normally be the blowing end is below, and the distal end is above. As a result, the player has to get used to upside-down fingerings.
One more flute-like pitched-noise instrument: Scraper Flutes are tubes made of medium-hard plastic with guiro-like ridges filed into the top surface. Using a short stick to scrape over the ridges, you get the guiro-like sound you’d expect, but with the tones of the pipe resonances highlighted. The scraping action agitates the walls of the pipe enough to excite an air resonance at a pitch determined by the pipe’s length. I’ve made these instruments in two forms: as individual tubes with tone holes to vary the pitch, and as tuned sets of tubes producing one note each through their differing lengths. If you don’t like working with plastic, you can take a cue from the late instrument maker Darrell DeVore and make a similar instrument with bamboo.
I group together all of the above-mentioned flutes under the term “agitation flutes”.
Here’s one more pitched-noise instrument, this one not flute-like. You know you can make a nice raspy sound by scraping a fingernail or some sort of plectrum over the teeth of a comb. Often (depending on the comb) the ear can recognize some identifiable pitch among the noisy scraping sound. This pitch, if it is present, is the pitch of the individual teeth behaving a little like tiny lamellaphone (kalimba) tines. If all the teeth are the same length and thickness, they should all produce more or less the same pitch, and this is the pitch you hear cumulatively when you scrape. But with most combs this pitched tone is to some degree masked by all the unpitched noise mixed in there. A while back I made a tuned set of about 30 combs covering over two octaves by filing the teeth of each comb to the length that gave the desired pitch. The combs were mounted on a soundboard for musical scraping. The noise component in the sound is of course very strong, and it’s fair to say that it’s a pretty irritating sound, but irritating in an interesting way.
All of the instruments described here – the combs especially – have the quality mentioned above, that their pitched qualities get buried and lost whenever the musical context is full or complex. Their appeal is most apparent in more spacious contexts when the listener can take in the tonal complexity without losing the thread.